Kavli Affiliate: Michael McDonald
| Summary:
This is the second paper in a series where we examine archival far-ultraviolet spectroscopy of 29 massive elliptical galaxies from the Far Ultraviolet Spectroscopic Explorer (FUSE) with modern methods. In the first paper, we performed SED modeling with aperture-matched photometry and analyzed the young and old stellar populations in these galaxies. In this paper, we report extinction-corrected O VI $λλ$1032,1038 $mathringrm A$ fluxes and upper limits for each galaxy, which we use to infer the rate at which gas is cooling through $10^5.5$ K via multiphase condensation of the galaxy’s CGM ($dotM_rm O,VI$) under the assumption of steady radiative cooling. By considering both Galactic and intrinsic extinction, we overwhelmingly find $dotM_rm O,VI$ to be larger than values found previously in the literature by a median of $sim 80%$. Additionally, we quantify correlations between $dotM_rm O,VI$ and star formation rates, classical luminosity-based X-ray cooling rates, and X-ray spectroscopic cooling rates. The results suggest that the efficiency of cooling from the $gtrsim 10^7$ K circumgalactic medium evolves with host mass, being suppressed by a factor of $sim 4$-$5$ more at the cluster scale than it is at the group and elliptical scales. In contrast, under the steady cooling assumption, cooling from $10^5.5$ K to the molecular phase appears to be suppressed by an order of magnitude, independent of mass, requiring turbulent mixing layers, thermal conduction, multiphase recycling, a bottom-heavy initial mass function, or some other additional physics to explain.
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